A gas turbine engine includes a core having a compressor fixedly joined to a turbine by a core rotor extending axially therebetween. At least one combustor, for example an annular combustor or a plurality of combustor chambers distributed around the core, are disposed between the compressor and the turbine and include fuel injectors. The fuel injectors may be joined to a fuel control valve which meters fuel into the at least one combustor during operation.
The compressor includes one or more stages of circumferentially spaced apart compressor rotor blades and cooperating compressor stator vanes through which air is channeled during operation for increasing the pressure thereof. The pressurized air is discharged from the compressor and mixed with fuel in the combustor and suitably ignited for generating hot combustion gas which flows downstream therefrom and through the turbine. The turbine includes one or more stages of turbine rotor blades circumferentially spaced apart from each other, with cooperating turbine nozzle vanes expanding the combustion gas and extracting energy therefrom.
The engine also includes a suitable controller for controlling the various components thereof over a large range of rotor speed and output power.
Examples of known gas turbines which are suitable for use as aircraft engines are disclosed in U.S. Pat. No. 5,694,760, incorporated herein by reference and U.S. Pat. No. 5,732,5469, also incorporated herein as reference.
Thus, it is generally know in the art to power turbines with gases expelled from combustion chambers. These gas powered turbines can produce power for many applications such as aeronautics, but also terrestrial power plants or as power sources of ships. In the gas powered turbine the fuel is combusted in an oxygen rich environment. In the very most cases, the fuel is a hydrocarbon fuel, i.e. the fuel on the basis of hydrocarbon compounds, such as methane, natural gas, gasoline or kerosene. Generally, these combustion systems may emit undesirable compounds such as nitrous oxide compounds (NOX) and carbon-containing compounds. It is generally desirable to decrease various emissions as much as possible so that selected compounds may not enter the atmosphere. In particular, it has become desirable to reduce NOX emissions to a substantially low level.
Various attempts have been made to reduce gaseous emissions of turbine engine combustors. For example, in US 2006/0156729 A1, a catalytic combustor and method for substantially eliminating various emissions is disclosed using a catalytic structure within a combustor chamber. Within the catalyst, the temperature of the air is increased to an auto-ignition temperature which ignites a further part of the fuel that is added later. To achieve a prescribed temperature of the catalysts, hydrogen gas is used during a start-up to power the gas turbine.
Such known gas turbine engines have the disadvantage that the catalysts are heavy and take up considerable space within the combustor chamber. Hence, the whole arrangement is bulky, heavy and complicated.
Hither to, turbine engine combustor size has been the result of a trade-off between antagonist requirements:    a) at low turbine engine power, the relatively low speed combustion kinetics require a large combustor to mitigate un-burnt hydrocarbon and carbon monoxide emissions.    b) on the other hand, at high turbine engine power, a small combustor is desirable to minimize nitrogen oxide emissions (NOX), since NOX formation, which takes place at high temperatures, is slower than combustion.
Current turbine engine combustors are a good compromise between low and high power requirements.
However, the quest for ever more fuel-efficient turbine engines paves the way to very high bypass ratio, and very high pressure ratio turbine engines. Such turbine engines exhibit high pressure and high temperature at combustor inlets during high power operations. This is detrimental to NOX emissions. In addition, environmental concerns have led, and are likely to lead, to more and more stringent NOX certification requirements.
It is an object of the invention to reduce turbine engine combustor emissions of turbine engines that are operated over a large output power range.
A further object of the invention is to reduce gaseous turbine engine combustor emissions without increasing the size or weight of the combustor.
It is a further object of the invention to reduce the size and weight of the combustor without a negative effect on turbine engine combustor emissions.
It is a further object of the invention to provide gas turbine engines with a high bypass ratio and a very high pressure ratio, but low NOX emissions.